Clemson has won 21 football games in the past two seasons, tying a school record. But the Tigers and their fans lost a piece of “Howard’s Rock” last week.

Just don’t expect that vandalism to dilute what the school calls the rock’s “mystical powers.”

About a half century ago, Frank Howard, Clemson’s head coach from 1940-69, received the marble-like slab as a gift from pal Samuel Columbus Jones, Clemson Class of 1919. A few years later, under Coach Howard’s order, that rock from California’s Death Valley was placed in Clemson’s Death Valley.

The Tigers soon started rubbing the rock for good luck before running down “The Hill” at the start of each home game.

Since then, many Clemson folks have credited the rock for a strong home-field edge that persists: The Tigers are 12-1 at Death Valley over the past two years, the only loss coming to South Carolina, 27-17, in last year’s regular-season finale.

Yet another painful blow has been inflicted on the orange-clad faithful. School officials announced Wednesday that a large chunk of the rock — about 15 percent of its mass — was removed by unknown culprits on June 3. The police are investigating this crime of flagrantly unsportsmanlike conduct.

Security has been tightened near the rock, which resides in a transparent case on an unharmed pedestal.

So the Tigers should still have plenty of rock to rub before playing Georgia in a season-opening, Death Valley showdown on Aug. 31.

Before touching it, though, they should recall what Coach Howard, aka “The Baron of Barlow Bend,” told his teams about that ritual:

“If you’re going to give me 110 percent, you can rub that rock. If you’re not, keep your filthy hands off of it.”

And while current Clemson coach Dabo Swinney is on a winning roll (except against the dreaded Gamecocks), if he wants to keep his job for long, he should recall what Coach Howard said when he was forced out of that job following a dismal 4-6 season:

“I retired for health reasons. The alumni got sick of me.”

But they kept his rock.